Hard freezes are expected this morning and Wednesday as severe cold settles into the Tampa Bay area, dropping temperatures into the 20s and 30s, putting farmers on alert and opening cold weather shelters.

Gov. Charlie Crist declared a state of emergency Monday because of the threat to the state's agricultural products.

Low temperatures this morning are expected to be in the 20s in most of the Tampa Bay area and the teens as far south as Hernando County. Even parts of Pinellas County, surrounded by warmer waters from the Gulf of Mexico, could see temperatures in the 20s.

In Florida, it's easy to forget what this kind of cold feels like, or what the basic precautions are. Meteorologists and county and fire officials have been issuing warnings all weekend, hoping to spread the word to the unprepared.

"With this kind of cold, people need to employ basic safety measures,'' said Jennifer McNatt, meteorologist with the National Weather Service in Ruskin. "Pets should be brought inside, plants need to be protected and people need to make sure heating devices are being used properly.''

Farmers are on high alert over predictions of a hard freeze, which occurs when temperatures drop to 27 degrees or below for at least three hours. While citrus may be hardy enough to weather the cold, strawberry and vegetable farmers have greater concerns.

"It's never been this bad this early in the season,'' said vegetable grower J.R. Holman of J.R. Farms in Zephyrhills.

The lows are likely to threaten or break temperature records at several locations around west-central Florida. The record low for Dec. 14 at Tampa International Airport is 27 degrees, set in 1962.

With the coldest weather still en route, Monday began ominously enough, with scattered rain and temperatures dipping into the 30s and 40s. The biggest culprit, however, was the wind.

Gusts approaching 40 mph were reported in several locations, a problem for motorists, particularly on bridges. There were several reports of holiday decorations and traffic cones being blown into roads, creating another driving hazard.

Strong winds whipping up tall waves kept five boats, including a cruise ship, waiting since early Monday to pass the Sunshine Skyway bridge.

The first ship in line had been waiting since 1 a.m. Monday near Egmont Key, 9 miles out from the bridge, and the vessels sat in limbo until winds dropped from 20 knots to at least 15, said Bridgett Wells, a search and rescue controller for the Coast Guard.

Officials feared the 10-foot waves and 30-knot gusts could slam a boat into the concrete, Wells said.

It was no picnic for cruise lines, either.

Geraldine Murphy, a snowbird who winters in Port Richey, said her brother, Richard Lane, was on the Carnival Inspiration cruise ship scheduled to dock Monday morning at Port of Tampa.

He called before 3 p.m. to tell her the captain had announced they were stuck. The ship finally made it into the Port of Tampa Monday night.

Beyond those issues, the Hills­borough County Public Works Department issued a warning Monday saying drivers could encounter black ice on roadways near agricultural irrigation during the freeze.

As the Tampa Bay region girds itself for the latest bout of cold, some residents are still reeling from the last time we saw these conditions.

The region still is showing signs of damage from the record stretch of freezing temperatures that happened late last winter, when grass, plants and even some trees succumbed to the cold.

Fortunately, most Florida plants are "root hardy," meaning they come back, said Marina D'Abreau, a residential horticultural agent for the University of Florida extension services for Hillsborough County.

"Sometimes plants need to go down, and when they come back, they're more resilient and healthy," she said.

Still, people should bring their plants in if they can, or cover them with cloth all the way to the ground. Strings of Christmas lights — "the cheapy, traditional kind, not the LED ones," D'Abreau said — also help create warmth underneath the coverings.

In a windy cold like this, though, it's very hard to keep plants warm, she said, even with coverings.

In a freeze with little or no wind, coverings can help trap radiant heat around the plants. But with the strong winds in this cold front, she said, that heat just blows away.